Rheostat



v 1 Y AZF. MARTIN 687628 RHEosTAT Filed May'lo, 1924 5 vsheets-shew; 1

HJM im ZSTTORNEY Oct. 16, 1928. 18,687,628

A. F. MARTIN RHEOSTAT Filed May 10, .1924 3 Sheets-Sheet 2 f 1&9' 5

JWM

Oct. 16, 1928. 1,687,628

A. F. MARTIN- RHEOS'TA'T Filed May 10,5 1924 5 sheets-shes: 3

46 y IN VEN TOR. @mW/@rim WM TQM/4 Patented st. 16, 1928.

UNITED NSTATES PATENT; oFFlcE.

ALLAN F. MARTIN, 0F ROCHESTER,NEW YORK, ASSIGNOR TO `BAUSCH & LOMB OPTI- GAI:A COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION `O1 NEW YORK.

ItHEosTAT.

Application ined May 1o,

This invention relates to electrical apparatus and more particularly to resistance means or rheostats, one object` of the invenfully described, .the novel features lbeing pointed out in the claims at the end of the specification. Y

In the drawings I Figure 1 is a top plan view of an apparatus embodying the present invention'.`

Figure 2 isa sectional elevation on lineV 2a2a in Figure 1. f A Figure 3 is a view similarto'Figu're 1 but `Withthe cover plate removed.

Figure 4 is a view similar showing interior parts in section also.

Figure 5 is a sectional plan vieW of details a()A on the, line 5a--5a in Figure 4.

Figure 6 is a sectional elevation onl the line (3a- 6a in Figure V5.

Figure 7 is a plan vievv 0f a portion; of the resistancemeans detached.

V Figure 8 is an venlarged sectional vievv on the line 828a in Figure y7 and f Figure 9 is a vdiagrammatic viewof the electrical connections. l Similar reference numerals throughout the several views indicate the same parts.

The vpreferred embodiment of the invention, herein disclosedfby Way of illustration, comprises a supporting means or frame including a base portion 10 and a cover plate 11, more particularly described hereafter.

The base portion 10 comprises a plate 12 of substantial ythickness and rigidity on which is carried a substantially square sheetmetal plate 18 having upturned marginal flanges 14and at the corners of the underside of'plate 13 are supports 14a ofrubber. or other Asoft material.

- Over the plate 13 is placed a layer of asbestos` 15er other insulatingmaterial on which rests the resistance means now to be described.

The resistance means comprises preferably to Figure 2 butv 1924. serial No. 712,245.

a resistance element of the usual or any suitable form of resistance `vvireor other material which is Wound progressively upon itself substantially in a plane and in the form of a comparatively thindisky 16 lying compactly against the sheet 15 of insulating material on the base.' The resistance element may be in sections having different resistances and may be of various cross sectional forms. In the present instance, however, the resistance element is in the form of a single rstrip or ribbon, 17, Figures7 and 8, of nickel-iron alloy'of uniform cross section, and the strip is rwound "spirally to afford a flat disk as shown. The adjacent windings maybe separated or insulated in any suitable manner, being in the present instance insulated 'from each other byan oxidized coating as'more particularly shown in Figure 8 Where 18 rep- The ribbon resents the insulating coating. is preferably Wound on a member or disk 19 V,of copper or other `conducting material with which the Vinner end of the resistance spiral is electrically connected as by-'fixing the exposedor uninsulated inner end' 20`of the ribbon in a kerf inthe` periphery of the disk for a purposehereafterfexplained. The resistance spiral is secured in place onthe insulating material 15 of the base by clips 21 onthe base projecting over `the periphery of the spiral and insulated therefrom in anysuitable manner. f

The contact means cooperating. with the kresistance means described abovecomprises,

preferably, an auxiliary frame having anglebars 22 connected in spaced relation by end Aplates 23, Figure 5. The bars22 extend centrally across the resistance spiral 16, resting upon insulating strips 23a laid on the latter and thebars are securedto the mainframe by means of bolts 24, Figure 4, passing vertically through their ends and through the base plates 12 and 13 and the cover plate 1.1. These bolts carry spacing sleeves 25 bearing at one end on top ofthe bars 22 and at `the other against a nut` 26 on the bolt by means of Which the rails are securely clampedto gthebase. Nuts 27 on the ends of the bolts secure the cover in place. v

The end plates 23 of vthe auxiliary frame I 1,05 have fixed therein buttons 28..of insulating material, Figure'5, injwhichare supported the ends of spaced guide rods .29 extending centrally across the Iresistance spiral and parallel `with the plane thereof.y These rods are preferably of conducting metalbeing `extended at one end through the cover plate 11 and provided with binding posts 30. A third binding postl, carried by and also insulated from the cover plate, is connected by means of a wire 32 with the conducting member 19, as at 33, Figure 3.

The cont-acts are carried by a carriage 34, Figures and 6, comprising lpreferably a pair of channel shaped parts 35 connected at their tops in spaced relation bya plate 36 of insulating material secured to the channels as by means of screws 37, Figure 3. The flanges of the channels embrace the respective guides 29 as shown and are preferably maintained in continuous electrical contact therewith l as by means of brushes'? sliding in sockets in the channel flanges, as well as by similar brushes 38 sliding in sockets in the web of each channel and pressed against the guides by the leail springs 39. At one end of each channel there is a socket extension 40 in which is carried a contact 41 for electrical contact' with the resistance means below. These contacts are at opposite ends of the carriage and are spring` supported lin the usual manner. Itis apparent from this construction that each Contact is in continuous electrical contact ,through its kdistance from member 19 to 'include a Vsupporting channel and guide 29 with the corresponding' binding post 30 and the contacts are suitably spaced in the direction of .sliding movement of the carriage so that yin the extreme positions of the `latter one contact engages with the periphery or outer windings of the resistance spiral or disk 19. The carriage has fixed in its to a plate 36 a stud 42 carrying a handle or knob 43 projecting through 4aslot 44 in the cover plate 1l and it is apparent that as the carriage'is slid on its guide by the handle, its contacts successively engage v the different windings ofthe resistance element and the central conductingmember 19. That is to say, the voltage supplied through binding post 31 tothe central -member 19 is transmitted unreduced through either contact while the latter is in engagement with the member 19 or in -a variably reduced `amount determined 'by lthe movement ofthe contact over the windings successively to a greater or less greater or l'less length ofthe resistance element.

The spaced arrangement and simultaneous movement of the pair of contacts disclosed in the present embodiment particularly adapt .the deviceforfthe vdiil'erential control ofa. pair of circuits, such, for example, as thelamp cir- I cuits of .a dissolving view projection apparatus. Such anva'pplication is illustrated schematically .in Figure 9, where 45 and 46 represent a pair of lampshaving one terminal n 'of eachconn'ectedwith one side 47 of a power g circuit, Ythe other side 48 of which is shown as 'connected with y'the binding post 3'1. Thelatwhile the other isin 'contact with the vcentral conducting member 'The latter are connected by wires 50 with the other terminals ot the lamps. of the carriage and contacts lines, the iull voltage is applied to lamp 46 while the full length of the resistance element is included in the circuit o1' lamp 45 so that the latter is effectively dimmed or cxtinguished. By moving carriage 49 towards the right, resistance is gradually cut out of the circuit otlamp 45' as successive windings oi the resistance element are engaged by the corresponding contact so that lamp 45 is gradually illuminated, the insulating coating of the windings being of course removed over the ,path of the contacts. Member 19 is preferably of such a diameter as to maintain lamp 46 at its full illumination while the illumination of lamp 45 is being' built up. At a suitable point, however, the Contact of lamp 46 leaves the opposite side of member 19 and passes successively over the windings of the resistance spiral so that the illumination of lamp 46 is reduced as that of lamp 45 is increased.` Finally the other extreme position is reached in which lamp 46 is fully energized and illuminated by engagement ot its contact with member 19, while `lamp 46 is extinguished by the movement of its contact to the periphery of the resistance spiral. The constructionthus effectively provides for the differential control of thecircuits in a substantially yproportional manner or, if desired, with retardation ofone relative to the other by the vmember 19 as described. Such retardation is afforded also to a degree by the greater lengths of `the windings at the periphery of the spiral. The construction isobviously simple, .requiring but few parts .of practical and inexpensive form.

I claim as my invention 1. A rheostatv comprising a conducting member, a resistance element wound about said conducting member substantially spirally in a plane. and a. conta-ct comprising a pair ott spaced element-s movable one over said plane toward and from the spiral axis in direct contact with `successive windings of said element and the other in contactwith said conducting element. H

2.1 A rheostat comprising a resistance element wound substantially spirally in a. plane. a conducting member electrically connected with an end of said element, a contact comprising a pair of spaced elements movable one over said plane in direct Contact, successively, and the other in contact with the windings .of said element and with said member,

In the position shown in :t'ull contact in an external circuit.I

3. A rheostat comprising ay resistance element Wound progressively upon itseltl substantially in a plane7 a conducting member adjacent the center of vsaid windings and electrically connected with an end of said element, a pair of contacts movable over said plane in electrical contact, successively, with the Wind.- ings of said element and with said member, and means for connecting said member and said contacts in an external circuit.

4. In a rlieostat, the combination ot sup-V porting means, a resistance 'element on said means Wound substantially spirally in a plane, a conducting member adjacent-the axis ot said spiral and electrically connected with an end of said element, a carriage mounted on said means Jfor sliding movement parallel with said plane, a pair of contacts on said carriage spaced from each other in the direction of movement thereof for successive electric-alV e contact With said windings and with said member, and means or'connecting said member and said contacts with an external circuit.

5. In a rheostat, a fram-e, a resistance element on said frame Wound spirally in a plane, a conducting disk about which said element is Wound With an end of the latter connected lelectrically With the disk, spacedfconducting guides on said frame parallel With said plane,

a carriage sliding on said guides, a pair of `contacts on said carriage Jfor` successive electrical contact with said disk and windings and each in electrical connection With one ot' said guides, said contacts being suitably spaced in the direction of movement for simultaneously engaging the periphery of said spiral and said disk, respectively, and means for connecting said disk and guides in an external circuit.

6. In a rheostat, a. frame, a spirally Wound resistance 4element upon the frame, a conducting member, a guide on said frame and a member including a pair of spaced contacts slidable upon the guide and one being adapted to successively engage the different windings` of said element and the other arranged to engage said conducting member.

7. In a rheostat, a frame, a -spirally Wound resistance element upon the frame, a conduct- .ing member about which said element is Wound and With which it is electrically con* nected, a circuit connection leading to said member, a conducting guide on said frame provided with a circuit connection, a carriage movable upon said guide in proximity to saidV resistance element, and sep arat-e contacts upon the carriage, one of which is adapted to move in engagement with the resistance element and the other in engagement with said conducting member.

ALLAN F. MARTIN. 

